Mosquitoes are the deadliest creatures in the world for humans due to their ability to transmit infectious diseases such as dengue fever. To find a mating partner, male mosquitoes form a swarm and wait for females to fly by. When a female enters this swarm, males use their sensitive hearing capabilities to listen for the sound of a female's flight tone, locate her, and then try to mate. Professor Azusa Kamikouchi and her research team at the Graduate School of Science, Nagoya University are focusing on this behavior, aiming to establish a method to control reproduction by targeting hearing in male mosquitoes.
In this study, the research team investigated the effects of serotonin, a major neurotransmitter, on the auditory function and behaviors of Aedes aegypti, a species of blood-sucking mosquito. The team first identified serotonin receptors that are strongly expressed in the auditory organs of mosquitoes. They also found that serotonin may control the function of the male mosquito's auditory organ through a receptor type called 5-HT7. This discovery is a world first.
The group then analyzed auditory function in male mosquitoes injected with serotonin-related compounds. To achieve this, the group used a laser Doppler vibrometer to measure the vibration of the mosquito's auditory organ, and found that the frequency of its vibration changed significantly after injection of compounds which alter the level of serotonin in the mosquito. Additionally, male mosquitoes treated orally with a serotonin synthesis inhibitor showed a marked decrease in approach behavior to sounds that mimicked the female's flight tone. These results indicate that serotonin controls the function of the auditory organ in male Aedes aegypti.
The team hopes that further research focusing on serotonin will lead to the development of new methodologies to control mosquito reproduction via targeting Aedes aegypti "ears." With the recent increase in insecticide-resistant mosquitoes, focus is sure to be placed on practical implementations of the team's R&D.
The relationship between hearing and serotonin in male mosquitoes
